Spacer implant for substituting missing vertebrae

Abstract

An implant for replacing a removed vertebra includes an outer sleeve having a longitudinal axis and a peripheral inner surface. The inner surface has a series of axially adjoining, peripheral grooves lending the inner surface a sawtooth-shaped configuration when viewing the inner sleeve in axial section. The implant further includes an inner sleeve having a longitudinal axis and a peripheral outer surface. The outer surface has a series of axially adjoining, peripheral ribs lending the outer surface a sawtooth-shaped configuration when viewing the inner sleeve in axial section. The inner sleeve is telescopingly received in the outer sleeve such that the series of axially adjoining, peripheral ribs of the outer surface engage into the series of axially adjoining, peripheral grooves of the surface in an interfitting relationship. The sawtooth-shaped configurations of the inner and outer surfaces are oriented such that in normal operation the sleeves are prevented by the interengaging sawtooth configurations from being telescoped into one another, but are allowed by ratchet action to telescope outwardly from one another. The inner sleeve is radially sufficiently resilient to allow alternating radial compression and expansion during the ratchet action.

We claim: 
     
       1. An implant for replacing a removed vertebra, comprising (a) an outer sleeve having a longitudinal axis and an inner surface having a periphery; said inner surface having a series of axially adjoining grooves each extending along a substantial part of said periphery; the groove series lending said inner surface a sawtooth-shaped configuration when viewing said outer sleeve in axial section; and   (b) an inner sleeve having a longitudinal axis and an outer surface having a periphery; said outer surface having a series of axially adjoining ribs each extending along a substantial part of said periphery of said outer surface; the rib series lending said outer surface a sawtooth-shaped configuration when viewing said inner sleeve in axial section; said inner sleeve being telescopingly received in said outer sleeve such that said series of ribs of said outer surface engage into said series of grooves of said inner surface in an interfitting relationship; said sawtooth-shaped configurations of said inner and outer surfaces being oriented such that in normal operation said sleeves are prevented by the interengaging sawtooth configurations from being telescoped into one another and are allowed by ratchet action to telescope outwardly from one another; said inner sleeve being radially sufficiently resilient to allow alternating radial compression and expansion of said inner sleeve during the ratchet action.   
     
     
       2. The implant as defined in claim 1, wherein said inner and outer sleeves are cylindrical and said grooves and ribs are ring-shaped. 
     
     
       3. The implant as defined in claim 1, further comprising axial slots provided in said inner and outer sleeves. 
     
     
       4. The implant as defined in claim 1, wherein said inner sleeve has opposite axial ends and said series of ribs extends from one of said ends; further comprising an axial slot extending in said inner sleeve from said one end. 
     
     
       5. The implant as defined in claim 1, wherein said inner and outer sleeves each have an open end and a closed end; said open end of said inner sleeve being situated inside said outer sleeve and facing the closed end of said outer sleeve; said closed end of said inner sleeve being situated externally of said outer sleeve. 
     
     
       6. The implant as defined in claim 5, said closed ends of said inner and outer sleeves carrying outwardly and axially oriented claws.